A longitudinal study of 400 adoptive and 200 nonadoptive families is proposed to address recent critiques of research aimed at identifying environmental influences on psychological adjustment. Specifically, we seek to confirm the existence of shared environmental influences on adolescent problem behavior, determine whether they are developmentally stable, and explicate the specific sibling and parent factors that underlie their effect. Participating families will consist of adolescent sibling pairs and parents who completed an extensive in-person mental health and psychological assessment three years prior to the proposed follow-up. The in-person follow-up assessment will focus on the siblings and their primary caregivers and closely parallel the intake assessment by including: 1) mental health, 2) substance use and abuse, 3) behavioral Jeviance, 4) family and sibling relations, 5) adoption-specific risk factors, 6) individual-level risk factors, 7) other environmental risk and protective factors, and 8) demographic factors. The focus of the data analysis will be on: 1) estimating the strength of shared environmental influences using standard behavioral genetic models, 2) determining whether parent characteristics are associated with adolescent outcome in adoptive families, where genetic mediation is controlled, 3) testing a developmental model of sibling effects based on the notion of "legitimization", and 4) determining whether specific environmental factors potentiate individual-level risk factors. Our large, representative sample of adopted adolescents also gives us an unprecedented opportunity to rigorously explore the adjustment of adopted individuals who had been placed in infancy. In this regard, we are especially interested in the adjustment of adopted individuals relative to nonadopted individuals, the contribution of adoption-specific risk factors to adoptee adjustment, and the effect of age on adoptees' concerns about birth background and ethnic identification.